Rocking toy, seat and the like



Dec. 5, 1967 J. w. GRONDSTRA ROCKING TOY, SEAT AND THE LIKE- Filed March 2, 1966 LINE SURFA at TERM/IVA N am SURFACE GENERA TING LINES F lg. 2.

THE 70 55 DETERMINED v In van/or Jan W Grands/r0 Attorneys United States Patent 3,356,412 ROCKING TOY, SEAT AND THE LIKE Jan W. Grondstra, 284 Arlington St., West Acton, Mass. 01780 Filed Mar. 2, 1966, Ser. No. 531,258 3 Claims. (Cl. 297-258) ABSTRACT OF THE DISCLOSURE This disclosure deals with a rocking horse or similar structure in which a pair of sets of strands is provided defining the origin and adjacent regions of substantially a hyperbolic paraboloid, the strands of the pair of sets crossing in substantially straight lines extending from points along the edges of the structure at one end thereof to points along the edges on the opposite side of the structure at the other end, with base members comprising rockers and the like.

The present invention relates to rocking toys, seats .and the like, being more particularly directed to novel saddlelike sitting surfaces generated by a plurality of juxtaposed and, in part, intersecting sets of linear strands defining highly desirable configurations.

While the art is replete with the rocking horses and similar toys of the past centuries, there is at least more current concern with such factors as safety, posture support, facile fabrication from new materials, and design appearance consonant with modern trends. Similar remarks apply to seats, in general, and it is to the primary objective of providing significant improvement along such lines in such structures that the present invention is directed.

An object of the invention, accordingly, is to provide a new and improved seating structure having, in summary, a novel saddle-like surface generated by intersecting sets of appropriately designed linear strands, the improved safety, support and other advantages of which are hereinafter more fully treated.

A further object is to provide such a structure that is adapted for employment, also, as a novel rocking structure for use as a rocking toy, .a reducing or training structure, or the like.

Other and further objects will be explained hereinafter and will be more definitely delineated in the appended claims. In summary the invention encompasses a saddlelike seating structure comprising a pair of sets of strands defining the origin and adjacent regions of a substantially hyperbolic paraboloid, the strands of the pair of sets crossing in substantially straight lines extending from points along the edges of the structure at one end thereof to points along the edges on the opposite side of the structure at the other .end, with the base members upwardly curved to constitute rockers.

The invention Will now be described with reference to the accompanying drawings, FIG. 1 of which is a perspective view illustrating the invention as applied to a preferred rocking toy embodiment, though clearly the seating structure may, as previously stated, be otherwise employed, as well; and

FIGS. 2 and 3 are explanatory graphs illustrating details of design construction of the structure of FIG. 1.

3,356,412 Patented Dec. 5, 1967 Referring to FIG. 1, the seating structure of the invention is shown comprising a pair of crossing sets of juxtaposed, spaced strands I and II defining the origin and adjacent regions of a substantially hyperbolic paraboloid. The hyperbolic paraboloid is described by the equation x z y b a 0 (l) where x is the longitudinal axis (FIG. 2); z, the transverse axis; and y, the vertical axis; this surface exhibiting saddle-like shape near the origin that is preserved no matter how far from the origin and in what way the surface is terminated. The hyperbolic paraboloid is a socalled ruled surface which means that the surface can be generated by straight lines. Advantage is taken of this fact in the structure of FIG. 1, by extending substantially straight-line strands 1 of the sets of strands I, II, between rigid transverse end members 3, 3', later described. The end members 3, 3 form the termination of the surface and offer a place for attachment of the strands 1. The strands 1 cannot just be attached at arbitrary points on the surface terminations; but, rather, the coordinates of such points where a line intersects the surface termination must be precisely calculated in order for the surface, generated by these lines, to describe substantially the hyperbolic paraboloid or saddle point. Because of the fact that the hyperbolic paraboloid shows symmetry with respect to the planes X=O and Z=0, only a quarter of the total lines need be calculated, several of which are shown in FIG. 2.

It will be observed that, in accordance with the invention, strands 1 of the set of strands I from, for example, points P P P etc. along the right-hand edge of the left-end surface-terminating member 3 (FIG. 2), are strung in spaced straight lines across the longitudinal axis X of the structure to respective points P P P etc. on the opposite or left-hand edge of the right-hand surface-terminating member 3. The members 3, 3' will be of substantially parabolic contour in the Y-Z transverse plane with the origins at the top; and the point P for example, near the top of the right-hand edge of member 3 (FIGS. 1 and 2), will connect by a strand 1 to a point P near the bottom or lower end of the left-hand edge of member 3. Similar remarks apply to the strands of set 11 that cross in the seating or origin region, as more particularly shown in FIG. 1.

In order to enable the most advantageous use of straight-line strands, as before intimated, the points of strand connection between members 3 and 3 must be rather critically determined. The details of such determination may be ascertained from a study of the graph of FIG. 3, showing one of the lines P P elonging to the set depicted in FIG. 2. For clarity, the Z-coorclinate has been omitted in FIG. 3. The coordinates of the points P P and R; will also be calculated. These latter three points lie on the intersections of the hyperbolic paraboloid with the planes Y=KX-L, Y=KXL and Y=Q, respectively. Due to the omission of the Z-coordinate in FIG. 3, however, these surfaces show up as lines. The parameters K, L and Q can now be altered so as to yield the most desirable orientation of the rigid members 3, 3' which serve as terminations for the surface-generating lines or strands 1. The projection of the terminations on the Z=O plane need not be straight lines. It is only necessary for the surface-generating lines or strands 1 to have substantially the hereinafter described spatial relationships in order that the surface near the origin be of the desired substantially saddle shape.

Let point P have coordinates X Y and Z point P the coordinates X Y and Z etc. The value of X is tentatively picked from a sketch such as FIG. 3, and the value of Y is picked such that Z becomes positive. Then from Eq. (1), above,

The coordinates of the point P are now completely defined. It can be shown that Since the coordinates of point P are only of interest when Z becomes negative, the initial value of Y has purposely been chosen such that the first value of Z is positive and so that, when the magnitude of Y is decreased, the value of Z approaches zero from the positive side. Calculations described by Eqs. (2) and (3), above, are repeated, with the magnitude of Y decreased for each repetition, until Z becomes less than or equal to zero. At this point, the first line of interest has been reached. The calculations are now continued as follows: X =X by symmetry from the sketch of FIG. 3. Y can now be calculated with Eq. (1). It can be shown that and Y =KX L. Use of Eq. (1), then yields the value of Z It can further be shown that and Y =KX L. Again using Eq. (1) this yields Z From FIG. 3 it is seen that Y =Q. It can be shown that The value of Z can now be obtained from Eq. (1). All coordinates of the points P P are now known. These calculations are now repeated, each time decreasing the magnitude of Y The repetition of these calculations are kept up until Y becomes greater than or equal to zero. At this point, there is no need for further calculations since enough lines are known to generate a quarter of the surface. The amount by which the magnitude of Y is decreased in each set of calculations determines how many lines are specified. The smaller the increments of Y the more lines are determined, and vice versa. The amount by which the magnitude of Y is decreased during each repetition of the calculations should be such that a proper .amount of generating lines are determined so that the generated surface substantially describes a saddle shape. Varying the value of X and the values of the parameters a, b and c of Eq. (1) will cause a change in the appearance of the surface with respect to its length, width and height, but the mathematical truth of Eq. (1) still shows that the surface near its origin appears saddle-shaped.

The projection on the plane Z=0 of the rigid members 3, 3' which form the terminations of the surface, as shown in the embodiment of FIG. 1, substantially follows the lines in FIG. 3 indicated by Y=KX-L,

=KXL .and Y=Q. In order for the saddle-shaped surface generated as above described by substantially straight strands 1, supported by rigid members 3, 3', to be used as a rocking apparatus, some sort of longitudinal base rocker members 2, 2', upwardly curved, need to be attached to the bottom ends of the rigid members 3, 3'. The projection of the rockers 2, 2' used in the embodiment of FIG. 1 on the plane Z:0, is substantially as shown in FIG. 3, where the rocker is indicated by the equation (YY +R)==P-X The projections of the rocker on the planes X :0 and Y=O are immaterial because the surface which supports the rocking structure is in general parallel to the plane Z=O of the saddleshaped surface when said structure is in a stable, motionless condition. The rockers 2, 2, of course, do not need to be separate members. They can be integrated with the whole rigid body of the structure in order to also provide support for the generating strands 1. Thus, in FIG. 1, certain strands in the vicinity of P (originating from points near the top or origin region of support 3) are connected to the base rocker 2 itself. For this purpose, the coordinates of point P may be readily calculated since point P FIG. 3, forms the intersection of the tobe-determined line with the rocker 2, as described by the line (Y-Y +R)=PX The projection of the rocker portion 2-2' of the structure on the plane Z=0 substantially describes a parabolic curve which has the advantage that the rocker flattens out near its extremities. This dampens the rocking motion making it very unlikely for said structure to flip over when in normal use by the proper user.

By providing taut stringing of straight-line strands 1 between rigid end member 3-3 and selecting a somewhat resilient strand material, such as Seine twine or the like, and by using approximately the relative height, length and other dimensions shown in FIG. 1 (wherein the immediate surface origin region or seat is about midway between, or at least well-within, the top and bottom of end members 3), front and rear protection to the user is alforded during rocking motion. Not only is firm seating and back and front support effected, with several possible points of grip or hold, but the tension of the strands may be maintained in view of the straight-line strand construction defining the geometrical saddle-like seating surface.

Though the above formulae enable any desired calculation of points of connection of strands 1, a highly suitable structure has been successfully operated as a rocking toy for children, having members 3 and 3' about 3.3 feet high and 1.1 feet apart at their bases and separated 1.6 feet along rockers 2-2. Twine strands were used in each of sets I and II, with a distribution and dimensioning closely paralleling that shown in FIG. 1.

Further modifications will also occur to those skilled in the art and all such are considered to fall within the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A saddle-like seating structure comprising a pair of sets of strands defining the origin and adjacent regions of a substantially hyperbolic paraboloid, the strands of the pair of sets crossing in substantially straight lines extending from points along the edges of the structure at one end thereof to points along the edges on the opposite side of the structure at the other end, the said edges at the said ends of the structure defining substantially parabolic surface-terminating members disposed in planes transverse to the longitudinal axis of the structure and with their origins at the top thereof and the said strands strung therebetween, the lower ends of said transverse members at each end of the structure being interconnected by a pair of longitudinal base members and said base members being upwardly curved to constitute rockers, with the strands from some of said points connecting with points of said rockers.

2. A structure as claimed in claim 1 and in which certain of said some points are disposed near the said top origins of the substantially parabolic surface-terminating members.

3. A structure as claimed in claim 2 and in which said strands are substantially straight-line resiliently deformable elements and said surface-terminating and rocker base members are substantially rigid, the strands UNITED STATES PATENTS 2,97s,704 4/1961 Cohen et a1. 52-81X 5 3,215,153 11/1965 Huddle 5280X 3,220,152 11/1965 Sturm 52--80X 6 Widmer 52-80 X Peake 52-80 X Kowalski 5121 Sturm 5281 X CASMIR A. NUNBERG, Primary Examiner. G. O. FINCH, Assistant Examiner. 

1. A SADDLE-LIKE SEATING STRUCTURE COMPRISING A PAIR OF SETS OF STRANDS DEFINING THE ORIGIN AND ADJACENT REGIONS OF A SUBSTANTIALLY HYPERBOLIC PARABOLOID, THE STRANDS OF THE PAIR OF SETS CROSSING IN SUBSTANTIALLY STRAIGHT LINES EXTENDING FROM POINTS ALONG THE EDGES OF THE STRUCTURE AT ONE END THEREOF TO POINTS ALONG THE EDGES ON THE OPPOSITE SIDE OF THE STRUCTURE AT THE OTHE END, THE SAID EDGES AT THE SAID ENDS OF THE STRUCTURE DEFINING SUBSTANTIALLY PARABOLIC SURFACE-TERMINATING MEMBERS DISPOSED IN PLANES TRANSVERSE TO THE LONGITUDINAL AXIS OF THE STRUCTURE AND WITH THEIR ORIGINS AT THE TOP THEREOF AND THE SAID STRANDS STRUNG THEREBETWEEN, THE LOWER ENDS OF SAID TRANSVERSE MEMBERS AT EACH END OF THE STRUCTURE BEING INTERCONNECTED BY A PAIR OF LOGITUDINAL BASE MEMBERS AND SAID BASE MEMBERS BEING UPWARDLY CURVED O CONSTITUTE ROCKERS, WITH THE STRANDS FROM SOME OF SAID POINTS CONNECTING WITH POINTS OF SAID ROCKERS. 